1. Field of the Invention
The present invention relates to a multi-SIM cellular telephone which allows a single cellular telephone to simultaneously access information stored on multiple Subscriber Identity Module (SIM) cards. The multi-SIM cellular phone thus has the capability of allowing the user access to more than one phone number on a single handset. The multi-SIM cellular phone also has a phone number assigned to the device itself so that communication to and from the phone can occur without knowledge of the specific subscriber phone numbers.
2. Description of the Prior Art
Cellular telephones are electronic devices used for full duplex two-way radio communication. Cellular service subscriber information is stored in a SIM embedded on a piece of plastic or other suitable material. Henceforth ‘SIM’ and ‘SIM card’ will be used interchangeably. Typically, one SIM card with a single IMSI is installed in any given mobile handset. This allows a handset user to have only one ‘phone line’ per handset at any given time.
U.S. Pat. No. 7,613,480 describes an invention that allows multiple service subscriptions to be encoded on a single SIM card. This is an upgrade from previous systems that allow only one subscription to be encoded and allows the user to access multiple service regions via software coding.
This design is limited in the fact that if the user chooses to port one subscription to another handset, then all subscriptions must be ported to the new handset (via the physical process of moving the SIM card from one handset to another). Also, it allows service providers to refuse service or to charge higher rates if the customer chooses to buy service on the second subscription from a service competitor. This design is not for a new phone or new way of doing business. For example, if one subscription has conference-calling capabilities and the others do not, then the invention described in U.S. Pat. No. 7,613,480 does not allow the user of the handset to automatically switch to the other line. Instead, the user would need to disconnect the call and have all conference attendees connect to the subscription with conference capabilities, thereby disclosing the phone number to all conference attendees. This deficiency decreases the privacy of the user of the handset. There is also no provision in U.S. Pat. No. 7,613,480 for the handset itself to be assigned a phone number and have calls to this number directed to any or all of the valid subscriptions installed on this phone.
U.S. Pat. No. 7,369,848 describes a means by which a person with a cell phone who is outside his/her home network is able to use a single SIM card in order to operate in either the home region or roaming region. The purpose of this invention is to provide a more seamless transition from home service to roaming service.
This invention is limited in that it requires cooperation between multiple service providers and it places priority on one subscription at a time. Thus, there is a ‘home’ IMSI and a ‘local’ IMSI. There is also limited portability of the subscriptions among different handsets. Furthermore, there is no provision in U.S. Pat. No. 7,369,848 for the phone that uses this invention to be assigned a number that is attached to the IMEI number of the handset. Therefore, all phone calls must be directed to a particular subscription rather than to the number associated with the phone itself.